Asphalt-impregnated kraft paper panel board



Oct. 25, 1955 R. H. WOOD 2,

ASPHALT-IMPREGNATED KRAFT PAPER PANEL BOARD I Filed Dec. 11, 1952 ljiolmm H Wood B ably sized and preferably hard sized.

United States Patent Ofiice 2,72 1,8 16 Patented Oct. 25, 1955ASPHALT-IMPREGNATED KRAFT PAPER PANEL I BOARD This invention relates towaterproof asphalt-impregnated multiply kraft paper boards.

Panel boards of this character have been used quite extensively in theautomobile industry and one important use has been on the inner side ofthe body providing a surface to which the fabric upholstery material isattached. The panel board heretofore in use for this purpose has notbeen entirely satisfactory for two principal reasons. In the firstplace, it has an exterior surface of outwardly protruding fibers, whichrub off on the workmans hands. The asphaltic impregnated fibers are suchas to come off on the workmans hands, which soil the upholstery when thelatter is applied to the panel or in mounting the upholstered panel inthe automobile body. In the second place, it is desired to sew theupholstery fabric to the panel, but this has not been satisfactorilyaccomplished because during the sewing operation, the needle picks upsome of the asphalt impregnant and then soils the fabric. The expense ofcleaning the fabric soiled in this way has been considerable.

It is a desideratum to overcome these difficulties and objections and toproduce a new and improved panel board, which has the desirablequalities of the waterproof asphalt board heretofore in use andadditionally, can be handled and sewed satisfactorily without soilingthe hands of the operator, the sewing needle, and of greatestimportance, the upholstery itself.

Other objects of the invention will hereinafter appear, and for thepurpose of illustration but not of limitation, an embodiment of theinvention is shown on the accompanying drawings, in which Figure l is anenlarged top perspective view partly in section, of a panel board;

Figure 1A is an enlarged portion of Figure 1, and

Figure 2 is an enlarged top perspective view of the board showing aportion of each individual ply folded back upon itself for purposes ofclarity.

The illustrated embodiment of the invention comprises a panel board Pwhich has great strength, rigidity, is water-resistant, and notappreciably afiected by changes in temperature and humidity, and is of amultiply asphaltimpregnated kraft paper structure. As shown, the boardis made up of three plies a, b and 0, although the number of plies maybe increased as desired. Each of the plies consists of a sheet of kraftpaper of suitable thickness, as for example .016 inch, produced fromsulphate pulp having cellulose fibers in a single layer extendingapproximately equally in all directions. Preferably, the cellulosefibers are continuous and relatively long.

In order to render the sheet water-resistant, it is suit- It should beunderstood that the exposed surfaces of the plies a and c are smooth andhard, obtained in any suitable manner as by calendering, whereas theinner or unexposed surfaces have outwardly protruding fibers. In otherwords, the two exposed surfaces of the panel board P are smooth and hardwith no protruding fibers, whereas the unexposed surfaces of the plieshave protruding fibers. These protruding fibers cooperate with anadhesive for bonding the several plies together. The adhesive is placedbetween the several plies and is absorbed by the board, the greatlyenlarged section of Figure 1 showing how the adhesive absorbs into theboard, following the fibers by capillary action for effecting anefiicient and satisfactory bond. A satisfactory adhesive for thispurpose may be a mixture of latex and starch paste, the lattercontaining Water as a solvent, although other adhesives may besatisfactory. It will further be understood that the panel board ispreferably subjected to some pressure to hold the plies together untilthe adhesive has had sufi'icient time to set.

Prior to the assembly of the sheets in superposed relation, each sheetis impregnated either completely or partially on the two sides withasphalt. I have found that asphalt applied at a temperature ofapproximately 450 F. aifords satisfactory penetration of the asphaltinto the kraft paper sheet. I desire that the asphalt upon cooling beexceedingly hard and brittle, so that it preferably should have amelting point of approximately 180 F. and a penetration point of fromzero to one. Such penetration point is determined by the standard methodof test for the penetration of bituminous materials as devised by theAmerican Society for Testing Materials, and is a test well-known tothose skilled in this art. According to this test, the result (1) wouldbe expressed in a degree, such degree being equivalent to .01 of acentimeter, which a standard needle will vertically penetrate a sampleof the material in five seconds under a load of one hundred grams, thematerial being at a temperature of 77 F.

With an asphalt impregnated kraft paper sheet having a penetration pointof zero to one, a needle penetrating the panel board for the purpose,for example, of sewing fabric upholstery material to the board, willactually punch out a hole through the material because of thebrittleness of the asphalt. This militates against any of the asphaltadhering to the needle and thereby soiling the upholstery fabric duringthe sewing operation. In this manner, one of the objectionable featuresinherent in panel board of this type heretofore in use, is clearlyobviated, and it is found empirically that a panel board of thisstructure with the asphalt impregnation of such a penetration point, canbe sewed without difliculty, and does not have the objectionable soilingor damaging characteristics so far as the fabric upholstery material isconcerned. With an asphaltic impregnant of the brittleness as abovespecified, the thread employed in the sewing operation is not stainedand by maintaining a clean thread during the sewing of the upholsterymaterial to the panel board, the desired cleanliness of the upholsteryis maintained.

The elimination of the protruding fibers from the exposed fiat surfacesof the panel board is a definite advantage in that it prevents stainingof the hands of the workmen and the consequent dirtying of theupholstery material. The smooth, hard finish on these surfaces, whichmay be achieved by the use of calendering rolls, dispenses with thefuzziness with its attendant objections. In order to secure the plies toeach other, the inner surfaces of the outer plies have the protrudingfibers which cooperate with the protruding fibers on both surfaces ofthe intermediate ply, to secure these plies properly together.

It is to be understood that numerous changes in details of construction,arrangement and operation may be effected without departing from thespirit of the invention, especially as defined in the appended claim.

What I claim is:

A panel board comprising a plurality of superposed sheets, each sheetbeing resistant to physical change in a wide range of temperature andhumidity conditions and being composed of sized fiber pulp consisting ofa singly formed layer of fibers of cellulose disposed substantiallyuniformly in all directions, each sheet being impregnated with asphalthaving a melting point of the order of 180 F. and a penetration pointnot exceeding 1, the exposed surfaces of the outermost sheets beingsmooth with the fibers thereof lying within the plane thereof, thesurfaces of the sheets between said exposed surfaces having protrudingfibers, and an adhesive extending into the body of the sheets throughthe protruding fibers and conjoining adjacent sheets, said melting andpenetration point characteristics of the impregnating asphalt providingbrittleness whereby a sewing needle passing through the 4 panel boardpunches out a hole therethrough, and adherence of the asphalt to theneedle and to thread employed therewith is precluded.

References Cited in the file of this patent UNITED STATES PATENTS1,694,523 White Dec. 11, 1928 2,073,894 Wood Mar. 16, 1937 2,278,146Moeller Mar. 31, 1942 2,299,144 Heritage et al. Oct. 20, 1942 2,448,357Craig et al. Aug. 31, 1948

